An X-ray apparatus comprises an X-ray tube for emitting X rays, and the like. It is used in a medical diagnostic apparatus such as a CT scanner. It is desired that the images of objects photographed by the CT scanner be improved in quality. In order to improve the quality of images, the X-ray apparatus is desired to increase the output of an X-ray tube increased.
Various types of X-ray tubes are available for use in X-ray apparatuses. One type is a rotary anode X-ray tube in which the anode target rotates. The rotary anode X-ray tube has a rotor that rotates by virtue of the rotating magnetic field generated by the stator coil that is arranged outside the tube. Thus, the anode target, which is coupled to the rotor, is rotated. When the X-ray output is to be increased, the anode target, for example, is rotated at high speed in order to avoid local heating of the anode target due to electron bombardment.
In recent years, the anode target is rotated at higher speeds in the rotary anode X-ray tube in order to increase the X-ray output of the X-ray tube.
To rotate the anode target at such high speed, the stator coil that imparts a rotation torque to the anode target, for example, is necessitated to be modified in specifications. The stator coil thus modified differs in the frequency and voltage of the drive power externally supplied to it. Hence, the drive-power-supply device that supplies the drive power to the stator coil is modified in specifications, in compliance with the modification of the stator coil. The X-ray tubes available on the market may be used, without being modified at all. In this case, the drive-power-supply device hitherto used is used without being modified.
As described above, the conventional X-ray apparatus has a drive-power-supply device that is selected in accordance with the type of the X-ray tube. Therefore, a variety of drive-power-supply devices must be provided. Hence, it is difficult to unify the specifications, as a result causing an increase of manufacturing cost.
A drive-power-supply device that can be used for the X-ray tube having a three-phase anode-rotating mechanism or a two-phase anode-rotating mechanism is known, as is disclosed in, for example, Jpn. Pat. Laid-Open Publication No. 2000-150193.
The conventional X-ray apparatuses differ in the structure and rotation speed of the rotating component, such as rotor. Inevitably, different drive-power-supply devices are used in different types of X-ray tubes. The drive-power-supply devices can hardly unified in specifications. This causes an increase of manufacturing cost.
An object of the present invention is to solve the problems described above, thereby to provide an X-ray apparatus in which a drive power fits for the stator coil can be supplied, regardless of the type of the X-ray tube, and a method of driving the X-ray apparatus.